Pulverized fuel feeder



Jan. W, 1933. c. M. BUCK PULVERIZED FUEL FEEDER Filed Dad. 18, 1930ATTORNEY- tion of a modification of the invention, and

Patented Jan. 10, 1933 UNITED STATES CHARLES; H. BUCK, OF BROOKLYN, NEWYORK PULVERIZED FUEL FEEDER Application filed December 18, 1930. SerialNo. 503,169.

This invention relates to devices for feeding pulverized material suchas coal, and it is especially useful in feeding a mixture of.

air and coal to a burner.

One of the primary objects of the invention is to make it possible tofeed the pulapproximately the same velocity throughout the stream.

When feeding a mixture of coal and air to a burner, the rate of feedmust, of course, be varied according to the rate at which it is desiredto fire the furnace. It will be apparent that there will be a widevariation in conditions between minimum and maximum rates of operation.It is one of the primary objects of the invention to secure uniformityand evenness of mixture and stream flow for all rates of firing. 1 w AMore particularly it is an object to secure the above advantages inconnection with a relatively low pressure feeder.

l accomplish the foregoing,'together with such other objects and.advantages as may hereinafter appear, or are incident to the invention,by means of a construction which I have illustrated in the preferredform in the accompanying drawing, wherein Fig. l is an end elevation ofmy improvedfeeder with portions thereof broken away to more clearly showdetails of the construction; Fig. 2 is a vertical section throughFig. 1. Fig. 3 is a partial side elevation and sec- Fig. 4 illustrates adetail of the modification of Fig. 3.

Referring now to the drawing the reference numeral 7 indicates a hopperor bin for the pulverized coal or similar material. This hopper has adischarge throat 8 which has a long but narrow discharge orifice 9through which a Wide thin stream of coalis delivered. In the throatimmediately above the discharge orifice 9 is an agitating roll" 10provided with toothed projections which serve to stir up the coal in thethroat. In order to prevent packing and resultant arching of the coal inthe hopper I provide the screens 11 and 12, each of which supports aportion of the Weight of the coal in the hopper whereby the total headof coal in the hopper is not effective to produce packing. These screensare described, illustrated andclaimed in my copending application SerialNo. 495,006, filed November 12th, 1930, for pulverized fuel feeder. Inaddition, I provide an aerating device 13, also shown in saidapplication, and which is in the form of a pipe or pipes whichcommunicate at their lower ends with the interior or bottom portion 14resting upon the screen 11, and which communicate at their upper endswith the interior of the hopper at a point above the normal level of thecoal. As coal is fed a quantity of air is drawn downwardly into theregion of the upper end of the throat which serves to aerate the coaland thus assist in preventing packing and arching. Immediately below thedis- 7 charge orifice is a fan casing or housing 15 which has an opening16 directly below and in line with the discharge orifice 9, such openingbeing of the same width as the discharge orifice. The fan casing orhousing is somewhat like a volute and the fan 17 is mounted in thecasing so that its periphery is closely adjacentthe portion of thehousing indicated at 18. The air inlet to the housing is indicated at'19 and the outlet 20 from the housing is in the form of a fiat wideconduit, the width of which corresponds approximately to the length ofthe slot, as does the length of the fan.

The fan and the roll 10 are rotated by any preferred means such as 1 thegearing diagrammatically indicated at 21.

The operation of the device is as follows: When the fan is rotatedcentrifugal force tends to throw the air between the blades outwardlyand since the wall 15 of the fan casing progressively approaches theperiphery of the fan so that it is fairly close to the periphery thereofat the point indicated at 22 and quite closeto the part 18, a current ofair is set up in the conduit 20 for the full width thereof, this currentbeing uniform across the entire section of the conduit. The current isdischarged into the conduit with substantial velocity, practically thatof the 199 velocity of the blade tips, because of the volute. Inconsequence of this there is a tendency to create a vacuum in thehousing above the fan, particularly in the neighborhood of the inlet 19,so that a current of air is drawn through the inlet into the housing.This current flows across the discharge orifice and the coal dropsthereinto, in part by gravity and in part by the suction of the current.The compartments between the blades of the fan are comparatively emptyin the re gion opposite the wall 18, but as they travel upwardly fromthat region, air admitted from the inlet 19 enters, as well as some ofthe coal, but is shortly thereafter discharged, producing eddies in thevolute, which, in turn, secure intimate admixture of the coal and air inthe volute. Since the volute decreases in cross section this intimateand uniform admixture of the coal and air is maintained to the point ofdischarge into the conduit 20. Thus the fan delivers a stream across thefull width of the conduit in which there is a uniform admixture of coaland air throughout, with all portions of the stream moving substantiallyuniformly, except immediately adjacent the inner faces of the conduitwhere eddying again occurs because of frictional contact. It will beapparent that the continuing discharge of the contents of thecompartments between the blades will maintain the coal in suspension inthe volute. Also that uniformity of feed through the discharge orificeand along its full length are also obtained. The uniformity of the flowof the current across the orifice and the instrumentalities whichprevent the packing and secure aerating of the coal in the hoppercooperate toward this result.

The device will operate with relatively low pressure and still securethe desired results. If a blower fan of the axial inlet type wereprovided, it would not be possible to obtain the uniformity desiredexcept with a relatively narrow conduit andthe fan would have to operateat higher pressures. I am enabled by the arrangement described todeliver a stream of great breadth, for the full width of the furnace ifdesired.

It might here be noted that certain features of'the fan or blowerarrangement herein disclosed are not a part of the present invention perse but are described and claimed in my copending application Serial No.646,882 filed December 12, 1932.

In the modification shown in Figs. 3 and 4 I provide a rotating heateror agitator 23 immediately below the discharge orifice to aid inmaintaining admixture. This agitator may be rotated in any preferredmanner as, for example, by the gearing 23a shown in Figure 4. Asillustrated in this figure, furthermore, the beater 23 includes aplurality of heater or agitator rods 23?) extended lengthwise for thefull length of the fuel discharge orifice. In the arrangement of Fig. 2some air may be admitted, preferably through the openings. 24 controlledby a disk shutter or the like.

' In'the preferred practice of my invention I thermolize crushed coal byheating it, preferably in inert gases, from a temperature substantiallyabove about 220 F. to approximately 450 F. The coal is subjected to thisheat treatment until the particles are brought to this temperaturethroughout. This drives ofi the lighter volatiles, satisfies thechemical affinities which produce autogenous combustion and renders thecoal non-explosive. This temperature, however, is insufficient toproduce thermal decomposition. The thermolized coal is then pulverized.

With the coal in this condition I am enabled to deliver it to thecombustion chamber with substantially all the air required forcombustion, at low pressure and at low velocity, by means of anapparatus such as shown and described.

lVith ordinary raw pulverized coal it has been found commerciallyimpractical to deliver the coal admixed with all of the air required forcombustion, for the reason that coal in such condition must beintroduced by a high pressure blast involving the use of a high pressurefan. It is expensive to produce such high pressure air. Thermolizedcoal, either because of low rate of flame propagation, or for some otherreason, can be introduced in a state of admixture with practically allthe air required for combustion and at velocity so low as to permit ofthe use of a low pressure fan-such as described. This makes a veryeconomical process for burning coal, besides having other advantages.-

The treated coal and process of treating the same, per se, hereinreferred to, are part of the subject matter of my copending applicationSerial No. 265,303, filed March 28th, 1928.

The method of burning pulverized coal herein referred to is describedand claimed in my copending application Serial No. 629,063, filed August16th, 1932.

I claim 1. In a pulverized coal feeder, a substantially volute-like fancasin terminating in an inlet opening at its larger end, a fan in saidcasing including a ring of fan blades mounted for rotation in a pathextended from the large end of the volute to the small end thereof, adischarge passage extended from the smaller end of the volute casing, I

and means for feeding powdered coal into the casing at a point adjacentits inlet end.

2. A pulverized coal feeder including a rotary fan, a generallyvolute-like fan casing wall substantially surrounding the fan "with oneportion thereof disposed closely adjacent to the path of movement of thefan from which point the wall progressively diverges, a relatively largearea air inlet in said Wall in the re 'on thereof spaced the maximumdistance rom the path of movement of the fan, a discharge opening insaid wall in its region of. minimum spacing from the path of movement ofthe fan, said discharge opening being of relatively small crosssectional area as compared to the inlet opening, and

means for feeding pulverized coal into the fan casing at a point in theregion'of the air inlet opening.

3. A. ulverizedcoal feeder including a rotary an, a generallyvolute-like fan casing wall substantially surrounding the fan i with oneportion thereof disposed closely adv jacent to the path of movement ofthe fan 7 from which point the wall progressively diverges, a relativelylarge area air inlet in said wall in the region thereof spaced themaximum distance from the path of movement of the fan, a dischargeopening in said wall in its region of minimum spacing from the path ofmovement of the fan, said discharge opening being of relatively smallcross sectional area as compared to the inlet opening, and means forfeeding pulverized coal into the fan casing at a point in the region ofthe air inlet opening, there being a casing part of relatively small.dimension circumferentially of the fan disposed closely adj acent to theath of movement of the fan and interposed; etween the inlet and thedischarge openings.

4. A pulverized coal feeder including a rotary fan, a generallyvolute-like fan casing wall substantially surrounding the fan with oneportion thereof disposed closely adjacent to the path of movement of thefan from which point the wall progressively diverges, a relatively largearea air inlet in said wall in the region thereof spaced the maximumdistance from the path of movement of the fan, a discharge opening insaid wall in its region of minimum spacing from the path of movement ofthe fan, said discharge opening being of relatively small crosssectional area as compared to the inlet opening, and means for feedingpulverized coal into the fan.casing at a point in the region of the airinlet opening, there being a casing part of relatively small'dimensioncircumferentially of the. fan interposed between the inlet and thedischarge openings and disposed closer to the path of movement of thefan than the casing wall at the opposite side of said discharge opening.

5. In pulverized coal feeding apparatus,

a fan including a ring of generally radially disposed fan blades, a fancasing wall spaced avconsiderable distance from the periphery of the fanatone point and rogressively approaching the periphery of the fan, meansfor feeding pulverized coal into the casing adjacent said point, aperipheral air inlet opening in said casing adjacent said point, aperipheral discharge opening in said casing in a region in which thecasing wall is relatively close to the periphery of the fan, and acasing part between said openings disposed closely adjacent to the fanperiphery, the area of said discharge opening and the area anddisposition of said casing part being so relatively arranged andproportioned that upon discharge of the coal and air from the fan underthe influence of centrifugal force, the resultant reduced pressurebetween the fan blades is maintained until the blades have passed saidclosely spaced casing part, whereby a negative pressure is produced inthe region of the air inlet.

6. A pulverized coal feeder including a fan having a ring of bladesmounted for movement in a generally circular path, a generallyvolute-like casing wall surrounding the periphery of the fan and closelyspaced with respect thereto at one side of the fan ascompared \toanother side thereof, a discharge conduit extended from the fan casinggenerally tangentially from a point in the region where the casing wallis relatively close to the periphery of the fan, an air inlet passageextended generally tangentially of the fan in a region in which thecasing wall is relatively widely spaced from the fan periphery, andmeans for feeding pulverized coal to the fan through the casing wall ata point intermediate the air inlet and the said discharge conduit.

7. A pulverized coal feeder including a fan having a ring of bladesmounted for rotation in a circular path, a generally volutelike casingfor the fan with its wall spaced a substantial distance from theperiphery of the fan in one portion thereof as compared to anotherportionthereof, means for introducing pulverized coal through the casingwall to the fan in a region in which the said wall is relatively widelyspaced from the periphery of the fan, a peripheral air inlet passage tosaid fan extended into the casing toward the coal inlet, the casingbeing substantially unobstructed between the air inlet and the point ofcoal; admission, and a peripheral discharge opening'in said casing inthe region in which the casing wall is relatively closely spaced withrespect to the periphery of the fan.

8. A pulverized coal feeder including a rotary fan having a ring offanblades mounted for movement in a generally circular path, the bladesbeing considerably elongated axially of the fan, a generally volute-likefan casing wall substantially surrounding the fan with one portionthereof disposed closely adjacent to the path of movement of the fanfrom which point the wall progressively diverges, a peripheral air inletto said fan formed through the casing wall in a region thereof which isspaced a relatively great distance from the path of movement of the fan,the length of the inlet opening being substantially equal to the axiallength of the fan, a peripheral discharge opening formed in the casingwall in a region in which it is positioned relatively close to the pathof movement of the fan, the length of the discharge opening also beingsubstantially equal to t e length of the fan, and means for feeding arelatively thin but wide sheet of pulverized coal into the fan casing ata point in the neighborhood of the air inlet, the length of the sheetalso being substantially equal to the length of the fan.

9. A pulverized coal feeder including a rotary fan having a ring of fanblades mounted for movement in a generally circular path, the bladesbeing considerably elongated axially of the fan, a generally volute-likefan casing wall substantially surrounding the fan with one portionthereof disposed closely adjacent to the path of movement of the fanfrom which point the Wall progressively diverges, a peripheral air inletto said fan formed through the casing wall in a region thereof which isspaced a relatively great distance from the path of movement of the fan,the length of the inlet opening being substantially equal to the axiallength of the fan, a peripheral discharge opening formed in the casingwall in a region in which it is positioned relatively close to the pathof movement of the fan, the length of the discharge opening also beingsubstantially equal to the length of the fan, the air inlet and thedischarge openings in said casing being arranged close to each othertoward one side of the fan, there being a fan casing wall partinterposed between the air inlet and the discharge openings ofrelatively small circumferential dimension disposed inclose proximity tothe path of movement of the fan blades, and means for feeding arelatively thin but wide sheet of pulverized coal into the fan casing ata point in the neighborhood of the air inlet, the length of the sheetalso lpeing substantially equal to the length of the In testimonywhereof I have hereunto signed my name.

CHARLES M. BUCK.

